Method and structure for variable-length frame support in a shared memory switch

Inactive Publication Date: 2002-12-26
IBM CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

0014] The major advantages of the approach according to the invention are the seamless integration, from a switching point of view, of unicast and multicast frames, and the cost-efficient merging of three highly desirable features into one switching fabric.

Problems solved by technology

A drawback of this approach is that the shared buffer must be at least as large as the largest frame to be switched, which is a rather undesirable and hardly foreseeable restriction.

Method used

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  • Method and structure for variable-length frame support in a shared memory switch
  • Method and structure for variable-length frame support in a shared memory switch
  • Method and structure for variable-length frame support in a shared memory switch

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Embodiment Construction

[0039] In the following more detailed description, the function of the invention will be described first. Subsequently, a hardware implementation will be disclosed. This description is supported and completed by the appended drawings which illustrate several examples, namely in:

[0040] FIG. 1 the system level architecture, already discussed above;

[0041] FIGS. 2a-2c the frame mode deadlock;

[0042] FIG. 3 an active concept unusable for multicast,

[0043] FIG. 4 a cyclic waiting multicast frame deadlock with two frames;

[0044] FIG. 5 a cyclic waiting multicast frame deadlock with three frames;

[0045] FIG. 6 an implementation for a logical output queue;

[0046] FIG. 7 a format for an output queue entry,

[0047] FIG. 8 a comparison of output queue size vs. implementation, and

[0048] FIG. 9 a shared memory with split control and data paths.

UNICAST DEADLOCK PREVENTION

[0049] First, it will be explained how to prevent deadlock conditions from occuring when only unicast traffic (traffic with only a sing...

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Abstract

The present invention relates to switching in electronic networks. Many data transmission protocols and technologies used in such networks, such as TCP/IP and Ethernet, use variable-length packets for transmission. Often however, the nodes that make up these networks typically contain high-speed cell switches that only support fixed-size data units. To support variable-length packets in such a fixed-size cell switch non-interleaving switching and transmission must be offered. The present invention provides such a solution in essence by segmenting a variable-length frame into a plurality of fixed-length cells including a start-of-frame cell, one or more continuation cell(s), and an end-of-frame cell and routes said fixed-length cells through said switch, thereby providing, at an output of said switch, subsequent and deadlock-free transmission of consecutive cells of a certain frame, and block any cell of a different frame from interleaving. This leads to better average delay characteristics and removes the need for packet reassembly.

Description

[0001] The present invention relates to switching in electronic networks. Many data transmission protocols and technologies used in such networks, such as TCP / IP and Ethernet, use variable length packets as their transmission units. However, the nodes that make up these networks typically contain high-speed cell switches that only support fixed-size data units. It would be desirable to support variable length data units in such a fixed-size cell switch by offering non-interleaving switching and transmission of such data units. This would remove the need for packet reassembly and lead to better average delay characteristics.[0002] Additionally, many such networks use so-called multicast, i.e. the duplication of one incoming data unit to multiple outputs, and Quality-of-Service (QoS) provisioning, i.e. service differentiation among classes of traffic, as important functions. Consequently, multicast and QoS support must today be offered by any switching fabric.INTRODUCTION AND PRIOR AR...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H04L12/54H04L12/70H04L12/931H04L12/933
CPCH04L12/5601H04L49/108H04L2012/5665H04L49/608H04L2012/5651H04L49/1538
Inventor COLMANT, MICHELGRAMSAMER, FERDINANDMINKENBERG, CYRIEL
Owner IBM CORP
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